The present invention relates to integrated circuit (IC) chips, and more particularly to an IC chip which includes an on chip detector that is capable of detecting particle emissions, e.g., alpha-particle emissions, from a nearby and/or distant particle emission source. The present invention also relates to a method of fabricating an IC chip which includes an on chip particle emission detector as one of the components of the chip.
The primary sources of alpha-particles in many IC chips are the solder balls such as C4 solder balls (Control Collapse Chip Connectors) used to connect the IC chip to an external substrate such as a ceramic package. In such cases, the alpha-particles must pass through the back end of the line (BEOL) of the IC chip to reach bulk silicon present therein. When an alpha-particle reaches the silicon, it will generate free electron-hole pairs in the silicon causing an electronic noise burst.
This electronic noise burst, in turn, may be detected by part of the IC chip and may be mistaken for a logic signal thereby leading to an error, which is oftentimes referred to in the art as a xe2x80x9csoft-failxe2x80x9d. This impingement of alpha-particles and eventual soft-fail problem has become more pronounced as the dimensions of the IC chips have been reduced.
In some circumstances, this soft-fail caused by alpha-particles leads to data corruption in or passing through logic circuits. By detecting alpha-particles passing through the BEOL, instances of soft-fail can be detected and the information so gathered may then be used to predict when failures may occur.
Although fail detection is well known and relatively simple for arrays of memory cells such as DRAM (Dynamic Random Access Memory), it is still very difficult, in terms of design, complexity, circuit area and performance impact, to detect soft-fails in logic circuits. It is however desirable to detect soft-fails in logic circuits to eliminate corrupt data, either by detecting it before soft-fail occurs or by destroying the data. In addition, recovery circuits or operations can be invoked such that the system containing the IC chip continues to run seamlessly.
In view of the above remarks, there is a continued need to develop a new and improved IC chip in which alpha-particles as well as other radiative particles can be quickly and easily detected so that soft-fail and other like errors can be determined, predicted and thus eventually eliminated. It would be extremely beneficial if a radiative particle detector could be fabricated as part of the IC chip itself so as to avoid substantially increasing the size of the IC package.
One object of the present invention is to provide an IC chip in which an on chip particle detector is formed between a particle emission source and circuitry in the chip that is adversely affected by impacts of particle emissions from the particle emission source.
Another object of the present invention is to provide an IC chip having a particle emission detector formed in the IC chip wherein said detector is capable of detecting particle emissions from a nearby and/or distant source as well as being able to output a signal to warn a user that particle emissions have been detected in the IC chip. This would allow a user to stop the use of the system containing the IC chip thereby permitting the system to recover from a potential soft-fail error.
A further object of the present invention is to provide a simple and relatively inexpensive method of fabricating an IC chip which contains an on chip particle emission detector as one of the integral components of the IC chip.
A still further object of the present invention is to use existing methods that are typically used in manufacturing and packaging of IC chips.
One aspect of the present invention relates to an IC chip which comprises an on chip particle emission detector that is capable of achieving the above and other objects. The on chip particle emission detector of the present invention is formed in the various wiring levels of the IC chip between the particle emission source and circuitry in the IC chip that is sensitive to particle emission. Specifically, in one embodiment of the present invention, the IC chip comprises:
at least one source capable of particle emissions;
circuitry formed in the IC chip that is adversely affected by impacts of particle emissions from said source; and
a particle detector formed in the IC chip between the circuitry and particle emission source for detecting particle emissions.
The particle detector of the present invention is a reverse biased Schottky diode that consists of a polysilicon layer having a depletion region formed therein and a patterned metal layer that is formed over the polysilicon layer.
In yet another embodiment of the present invention, the particle emission source comprises a lead solder ball that is formed on a surface of the IC chip, and the solder ball is capable of emitting alpha-particles.
In still another embodiment of the present invention, the particle emission detector is connected to a sense and bias circuit that is capable of monitoring the IC chip during use. The sense circuit may provide a signal when the particle detector senses a radiative particle thereby allowing for the stoppage of the system containing the IC chip.
In an even further embodiment of the present invention, the source of particle emissions is remote, i.e., distant, from the IC chip. This embodiment of the present invention is typically employed in cases wherein cosmic ray collisions, gamma rays and photon bursts are to be detected. In such an embodiment, the source of particle emissions is not built into the IC chip. Instead, it is some remote distant therefrom, yet the particles so emitted are capable of reaching an IC chip of the present invention and affecting it in the manner indicated above.
In other aspect of the present invention, a method of fabricating the above mentioned IC chip is provided. Specifically, the method of fabricating the inventive IC chip comprises the steps of:
(a) providing an IC chip having at least one layer of particle sensitive circuitry formed therein;
(b) forming another layer having at least one particle sensor region situated therein on a surface of said IC chip; and
(c) optionally, forming at least one particle emission source over said another layer.